Sewage and Effluent Treatment

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Sewage and Effluent Treatment

• 2-4 November 2002
• Seán Moran
• -The first few slides

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Day One 2 November 2002

• Overview Wastewater Engineering
• Wastewater Characteristics
• Wastewater Treatment Considerations
• Overview Wastewater Treatment Plant Design
• Physical, Chemical and Biological Processes

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Overview Wastewater Engineering

• Wastewater Treatment
• Wastewater is the water used by a community
• Collected and treated prior to discharge
• Standards of treatment vary but are generally
  becoming more stringent
• Treatment is a process of removal of smaller and
  smaller particles

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Overview Wastewater Engineering

• Sludge Treatment
• Sludges are the product of biological treatment
  of wastewater
• Sludges comprise solids found in wastewater plus
  organisms used in the treatment process
• Disposal is a major issue
• Various disposal techniques are used but each has
  advantages and disadvantages

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Overview Wastewater Engineering

• Water Disposal and Re-Use
• Wastewater treatment generates a Cleaned Water
  Stream
• Cleaned water is often discharged to a larger
  body of water for dilution
• Alternatively, cleaned water my be re-used for
  irrigation or rarely drinking water production

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Wastewater Characteristics

• Characteristics are normally estimated by
  empirical methods
• Wastewater Flows
• Flows arise from households, industry,
  infiltration and storm flows
• Flows are considered in both hydraulic and
  process design
• Levels of treatment may vary for different
  flowrates

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Wastewater Characteristics

• Wastewater Flows
• There is a variety of methods for estimating
  flowrates
• However there may be great variability in the
  factors which affect flowrates from region to
  region
• Different multiples of the Dry Weather Flow will
  receive each level of treatment

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Wastewater Characteristics

• Wastewater Composition
• Key design issues
• Solids density, particle size, level of Volatile
  Suspended Solids
• Biochemical Oxygen Demand
• Temperature
• Ammonia
• Nutrient levels

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Wastewater Characteristics

• Wastewater Treatment Considerations
• Objective to maintain or improve the quality of
  the receiving body of water
• Treatment stages
• Preliminary
• Primary
• Secondary
• Tertiary

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Wastewater Characteristics Classification of
Methods
Physical Processes Chemical Processes Biological Processes
Screening Sedimentation Filtration Precipitation Chlorination Aerobic Anaerobic
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Wastewater Characteristics

• Applicability and Selection of Methods
• Different processes are used to treat wastewater
  depending on the contaminants present
• Similarly, different processes are used to treat
  sludges, depending on the objective of treatment

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Overview Wastewater Treatment Plant Design

• Flowrate and Mass Loading
• Wastewater feed is not specified, therefore the
  plant must be able to treat whatever the
  wastewater contains
• Plant design will take account of historical
  flows and loadings, but must also be able to deal
  with expansion
• Plant must also be able to deal with a range of
  flow and load conditions, plus peak upstream flow
  conditions (eg storms)

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Overview Wastewater Treatment Plant Design

• Selection of Design Flowrates
• Domestic based on a flow per head. Varies
  between countries
• Industrial Based on records of discharge
  consents and of metered supplies
• Infiltration/Exfiltration based on a of the
  domestic flow
• Peaking Factors Depends on size of community

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Overview Wastewater Treatment Plant Design

• Selection of Design Flowrates
• Upstream Flow Equalisation
• Plants are not normally designed to treat total
  peak arisings
• Instead, hydraulic controls will direct flows
  above plant capabilities to storm system on
  larger works

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Overview Wastewater Treatment Plant Design

• Selection of Design Flowrates
• Upstream Flow Equalisation
• UK maximum flow to treatment plant is determined
  by Formula A
• Formula A PGEI1360P2E l/d
• Ppopulation
• Gaverage daily consumption per head l/h/d
• EIndustrial commercial discharges to sewer
  l/d
• Iinfiltration l/d

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Overview Wastewater Treatment Plant Design

• Selection of Design Flowrates
• Upstream Flow Equalisation
• For larger works with storm tanks, only Full
  Treatment Flow (FTF) will receive full
  treatment.
• FTF3PG3EI
• Formula A-FTF will pass to storm tanks

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Overview Wastewater Treatment Plant Design

• Selection of Design Mass Loadings
• Average mass loadings for BOD and Suspended
  Solids are commonly determined by Population
  Equivalent (PE)
• Design mass loadings are more complex and must
  take account of seasonal, diurnal and industrial
  load variations